fix(gui): closing the window always hides to the tray

It quit when there was no tune to keep applied, which looked like the
tray app stopping (always the case for a read-only window). Exit in the
tray menu quits; a balloon says so the first time the window closes.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: Rovey

README.md

@@ -44,7 +44,7 @@ That builds two programs in `.\build\Release\`: `GpuAutoOptimizer.exe`, the wind
 
 Start `GpuAutoOptimizer.exe`. The **Dashboard** shows the GPU with live telemetry, what is applied right now next to the saved tune (with **Apply saved tune**, the **Apply at logon** switch and **Revert to stock**), the four profiles and a log of what happened. On the **Optimize** page, pick a profile and press **Optimize GPU** (it offers to restart as administrator first, because tuning writes clocks and power limits). The run shows temperature, power and every probe as it happens; **Abort** restores stock. The results compare before and after and can turn on apply at every logon.
 
-With apply-at-logon on, Windows starts the app in the tray at every logon. It applies the saved tune and then keeps it applied: every 30 seconds it reads back what the driver reports. If the tune was reset (a driver reset or TDR), it applies it again; if that happens four times within an hour it stops and tells you the tune is probably not stable; if another program such as MSI Afterburner changed the settings, it leaves them alone and tells you; after a driver update it does not apply the old tune and tells you to optimize again. While it keeps a tune applied (or a run is in progress), closing the window keeps it in the tray and **Exit** in the tray menu quits; otherwise closing the window quits. **Revert to stock** in the tray menu, or `gao --reset` from a shell, puts the card at stock and the watchdog leaves it there until you apply the tune again (window, tray menu or `gao --apply`). Only one optimize runs at a time, from the window or the command line.
+With apply-at-logon on, Windows starts the app in the tray at every logon. It applies the saved tune and then keeps it applied: every 30 seconds it reads back what the driver reports. If the tune was reset (a driver reset or TDR), it applies it again; if that happens four times within an hour it stops and tells you the tune is probably not stable; if another program such as MSI Afterburner changed the settings, it leaves them alone and tells you; after a driver update it does not apply the old tune and tells you to optimize again. Closing the window keeps the app in the tray; **Exit** in the tray menu quits. **Revert to stock** in the tray menu, or `gao --reset` from a shell, puts the card at stock and the watchdog leaves it there until you apply the tune again (window, tray menu or `gao --apply`). Only one optimize runs at a time, from the window or the command line.
 
 ### The command line
 

docs/hardware-checks.md

@@ -60,7 +60,7 @@ root; adjust the path for a Debug build.
 | 34 | Watchdog backs off from another tool | tray running, set an offset in MSI Afterburner and Apply | no | a balloon says another program changed the settings; the watchdog does not fight it | |
 | 35 | One instance | start the app twice | no | the second start brings the first window forward and exits | Pass (2026-09-27, after the P5 fix pass): the second start exits with code 0, the first keeps running. |
 | 36 | CLI and tray side by side | tray running with the tune kept applied; `gao --reset`, wait 45 s, `gao --status`; then `gao --optimize` from a shell while the window runs an optimize | yes | after `--reset` the card stays at stock (the tray notes it and does not re-apply); after `gao --apply` the tray keeps the tune applied again; the second optimize refuses with `another optimize is already running` | Pass for reset and apply (2026-09-27): after `gao --reset` the card stayed at stock for 45 s with the tray running (no watchdog line); `gao --apply` applied the tune again. Two optimizes at once not yet tried. |
-| 37 | Closing the window | close the window with no tune applied, then again with a tune kept applied | no / yes | without a tune the app exits; with one it hides to the tray | Pass without a tune (2026-09-27): the app exits on close. |
+| 37 | Closing the window | close the window, then choose Exit in the tray menu | no | closing hides the window to the tray (a balloon says so the first time); Exit quits | |
 
 ## Notes
 

src/app/gui/main_gui.cpp

@@ -80,6 +80,7 @@ struct App {
     bool watch = false;   // keep the saved tune applied (off after a revert or a reset by choice)
     bool worker_was_running = false;
     bool strike_pending = false;   // a logon apply whose 2-minute grace has not passed yet
+    bool told_about_tray = false;  // the "still running in the tray" balloon, once per session
 
     // Crash dumps are written by a thread created up front (a crashing thread
     // may have no stack or heap left to do it itself).
@@ -539,13 +540,13 @@ LRESULT CALLBACK wnd_proc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {
             return 0;
         }
         case WM_CLOSE:
-            // With a tune to keep applied, or a run in progress, the window
-            // hides and the tray stays. Otherwise there is nothing to stay for.
-            if (g.watch || g.worker->running()) {
-                ShowWindow(hwnd, SW_HIDE);
-                g.visible = false;
-            } else {
-                g.exit_requested = true;
+            // Closing hides to the tray, like other tray apps; Exit in the tray
+            // menu quits. Say so the first time, or it looks like a quit.
+            ShowWindow(hwnd, SW_HIDE);
+            g.visible = false;
+            if (!g.told_about_tray) {
+                g.told_about_tray = true;
+                tray_icon(NIM_MODIFY, nullptr, L"Still running in the tray. Right-click the icon and choose Exit to quit.");
             }
             return 0;
         case WM_TIMER: